102 W. M. DAVIS RELATION OF GEOGRAPHY TO GEOLOGY 



IMPLICIT EXPLANATIONS IN GEOGRAPHICAL TERMS 



In view of the foregoing, I am disposed to maintain the truly geo- 

 graphical nature of the description, beginning with : "The Front Eange 

 is a highland of disordered and generally resistant crystalline rocks," and 

 ending with, "submaturely dissected by normal submature and mature 

 valleys, the higher parts of which have recently been strongly glaciated." 

 Its object is geographical throughout, in the sense that it strives to pre- 

 sent a truthful picture of the existing mountains. It is geographical for 

 just the same reason that a geographical quality is found in the phrases : 

 "Here is a dissected volcano,"" "there is an uplifted and slightly dissected 

 delta," "that is a peneplain, uplifted and gently tilted, maturely dissected 

 and recently heavily glaciated." Indeed the description of the Front 

 Eange is geographical for the same reason that the still shorter phrases, 

 ^Tiere is a delta," "there is a volcano," "that is a peneplain," are geo- 

 graphical. True, the description of the Front Eange was' much longer 

 than the brief, four-word phrase last cited; true, the description of the 

 Front Eange made repeated and explicit mention of various rock struc- 

 tures and past processes, while rock structures and past processes are only 

 implicitly suggested in such phrases as "this is a delta," "that is a vol- 

 cano," "there is a peneplain." But the longer description and the shorter 

 phrases are all geographical because their object is the description of 

 existing features of the earth's surface. In this case and everywhere else 

 it is the object in view and not any distinction between bre\dty and 

 length, or between the implicit and explicit mention of rock structures 

 and past processes, that should serve to determine whether a description 

 belongs under geology or geography. 



We may indeed fairly insist that if the description of the Front Eange 

 is not geographical, then the familiar geographical term% delta, volcano, 

 and peneplain, must also be withdrawn from geography, and that is mani- 

 festly absurd. There can surely be no question that these terms imply 

 structure and process. When we say "delta" we do not mean merely low 

 land near a river mouth ; there is abundance of low land near river mouths 

 along the Gulf coast of the Southern States that can not be included 

 under this term. Whatever delta may have originally meant, it surely in 

 this modern day means a deposit of river-brought land-waste, laid down 

 with suggestive form and a highly significant stratified structure in rela- 

 tively quiet water at a river mouth, where the efficiency of the river as a 

 transporting agent is rather suddenly decreased; and, furthermore, a 

 delta, thus understood, is perfectly well known not to be the product of a 

 momentary action; its production has required a significant measure of 



